In magnetic recording systems, information is stored in magnetic media that includes a layer of grains of magnetic material. Superparamagnetic instabilities become an issue as the grain volume is reduced in order to control media noise for high areal density recording. The superparamagnetic effect is most evident when the grain volume V is sufficiently small that the inequality KuV/kBT>70 can no longer be maintained. Ku is the material's magnetic crystalline anisotropy energy density, kB is Boltzmann's constant, and T is absolute temperature. When this inequality is not satisfied, thermal energy can demagnetize the stored data bits. Therefore, as the grain size is decreased in order to increase the areal density, a threshold is reached for a given material Ku and temperature T such that stable data storage is no longer feasible.
The thermal stability can be improved by employing a recording medium formed of a material with a very high Ku. However with the available materials, magnetic recording heads are not able to provide a sufficient or high enough magnetic writing field to write on such a medium. Accordingly, it has been proposed to overcome the recording head field limitations by employing thermal energy to heat a local area on the recording medium before or at about the time of applying the magnetic write field to the medium. By heating the medium, the Ku or the coercivity is reduced such that the magnetic write field is sufficient to write to the medium. Once the medium cools to ambient temperature, the medium has a sufficiently high value of coercivity to assure thermal stability of the recorded information. Heat assisted magnetic recording (HAMR) allows for the use of small grain media, which is desirable for recording at increased areal densities, with a larger magnetic anisotropy at room temperature to assure a sufficient thermal stability. Heat assisted magnetic recording can be applied to any type of magnetic storage media, including tilted media, longitudinal media, perpendicular media and patterned media.
Heat assisted magnetic recording requires a thermal source be brought into close proximity to the magnetic writer. The HAMR designs utilize an intense near field optical source to elevate the temperature of the media. When applying a heat or light source to the medium, it is desirable to confine the heat or light to the track where writing is taking place and to generate the write field in close proximity to where the medium is heated to accomplish high areal density recording. In addition, for heat assisted magnetic recording (HAMR) one of the technological hurdles to overcome is to provide an efficient technique for delivering large amounts of light power to the recording medium confined to spots of, for example, 50 nm or less. A variety of transducer designs have been proposed for this purpose.
Several methods to deliver the light into the optical elements on the optical/magnetic slider have been considered. These methods include laser on slider, free space, and fiber to slider. Laser on slider is viewed as a possibility for future generations, but requires unique laser diodes and creates a high thermal load on the slider. The free space delivery has made rapid progress using a grating to couple the light into a waveguide on the slider. Fiber to the slider has been tried using a polarization maintaining (PM) fiber having a 125 micron thickness. However, the thickness of the fiber caused unacceptable forces on the slider and the head required extensive active alignment.
During the telecom explosion of the past few years a number of specialty fibers were developed. In order to minimize bending losses and allow smaller package sizes, very thin low stiffness fibers were developed. These fibers had diameters from 60-85 microns, which reduced their stiffness by almost a factor of ten. Also polarization maintaining (PM) fibers were developed that were mechanically keyed to place the PM axis at a specified angle to a mechanical datum in the fiber mount.
There is a need for heads that can provide fiber on slider light delivery without the need for active alignment of the optical components. Such heads can be used in heat assisted magnetic recording or optical recording devices.